[exim] debugging a lookup

Im still trying to get my multi smarthost lookup working :-((
Ive started from a gmail login that works and am working from there

   router
send_via_gmail:
    driver = manualroute
    domains = ! +local_domains
    transport = gmail_smtp
    route_list = gmail-smtp.l.google.com

transport

gmail_smtp:
    driver = smtp
    port = 587
    hosts_require_auth = gmail-smtp.l.google.com
    hosts_require_tls = gmail-smtp.l.google.com

   authenticator
gmail_login:
    driver = plaintext
    public_name = LOGIN
   # client_send = : mx@??? : xxxxxx
client_send =   :
"${extract{auth_name}{${lookup{$sender_address}wildlsearch{/etc/exim4/smtp_users}{$value}fail}}}" 

: xxxxx

I can login and send with the text version of the client_send line

exim -be
'${extract{auth_name}{${lookup{mx@???}wildlsearch{/etc/exim4/smtp_users}{$value}fail}}}'
returns the correct login email address name from the file
and

exim -be
'${extract{auth_pass}{${lookup{mx@???}wildlsearch{/etc/exim4/smtp_users}{$value}fail}}
returns the password in the lookup file ,which is

root@server:~# cat /etc/exim4/smtp_users
*@gmail.com: smarthost="smtp.gmail.com::587"
auth_name="xxx@???"    auth_pass="xxxx"

but substituting the email address with the lookup
client_send = :
"${extract{auth_name}{${lookup{$sender_address}wildlsearch{/etc/exim4/smtp_users}{$value}fail}}}"

: xxxxx

get this in the log file

2011-12-11 20:34:06 1RZpzq-0005VR-0x gmail_login authenticator failed
H=gmail-smtp.l.google.com [209.85.225.108] 535-5.7.1 Username and
Password not accepted. Learn more at
535 5.7.1 http://mail.google.com/support/bin/answer.py?answer=14257
zs7sm35451165igb.0
2011-12-11 20:34:06 1RZpzq-0005VR-0x == pdc124@???
R=send_via_gmail T=gmail_smtp defer (-42): authentication required but
authentication attempt(s) failed

how can i debug this further to see where the problem is ?